Syrian state television says Mr Halqi was unharmed in the blast in the Mazzeh district of the capital.

"The terrorist explosion in al-Mezze was an attempt to target the convoy of the prime minister," it said.

The Britain-based Syrian Observatory for Human Rights says one of Mr Halqi's bodyguards was among the six people killed.

The observatory, which is opposed to the regime of president Bashar al-Assad, says the convoy appears to have been targeted by a remotely-detonated car bomb.

State television says the explosion happened near a public garden and a school in the neighbourhood, a well-secured district that is home to embassies, government buildings, intelligence facilities and several political figures.

"I was walking in the street when suddenly there was a very powerful explosion and I saw a car burning and people running," a young man told AFP at the scene.

"I heard glass shattering," he added, saying he had tried to hide for fear a second explosion would follow.

Moscow's words and actions — including the alleged poisoning of a former spy — are not the results of random aggression but rather fall into distinct patterns that can help us anticipate Russia's next moves under Vladimir Putin.